Active weather spread into the Eastern U.S. on Sunday as a low pressure system lifted northeastward across the Ohio Valley toward the Lower Great Lakes and Northern Appalachians. As this system progressed, moisture from the Gulf of Mexico spread across the Southeast, Mid-Atlantic, and into the Eastern Valleys. This translated into continued scattered showers and thunderstorms ahead of the low pressure system in parts of southern Michigan, the Ohio Valley, and the Mid-Atlantic. More organized rain and thunderstorm clusters formed ahead of an associated cold front trailing from the low across the Tennessee Valley through the Lower Mississippi Valley. While severe thunderstorm development was not expected ahead of this frontal boundary, moderate instability led to sufficient risk for isolated large hail and/or damaging wind gusts. Heavy rain from today and yesterday led to Flood Watches and Warnings as well as Flash Flood Warnings in parts of Tennessee, northern Georgia, and western areas of the Carolinas.

Meanwhile, behind this activity, a pair of cold fronts dropped across the Northwest and North-Central U.S., kicking up areas of scattered rain showers and isolated thunderstorms from the Pacific Northwest through the Upper Mississippi Valley.

Temperatures in the Lower 48 states Sunday have ranged from a morning low of 21 degrees at Alamosa, Colo. to a midday high of 102 degrees at Thermal, Calif.